This invention relates to dielectric compositions, and more particularly, to titanate compositions.
Discrete capacitors comprise a shaped sintered dielectric object (e.g., a disk) on which electrodes have been sintered. Leads are attached to the electrodes. The capacitors are often based upon the perovskites barium titanate and substituted barium titanate. Barium titanate sinters at high temperatures (about 1400.degree. C.); various other titanates are sintered at high temperatures and/or in special atmospheres. Thus, N. N. Krainik et al. (Soviet Physics-Solid State, 2, 63-65, 1960) report solid solutions between, inter alia, PbTiO.sub.3 and PbMg.sub.0.5 W.sub.0.5 O.sub.3. Apparently a wide range of compositions, with 0-80% PbTiO.sub.3, was investigated (see FIG. 2 thereof). Firing was carried out in an atmosphere of PbO vapor, which precludes practical commercial applicability. No suggestion was made as to the manufacture of multilayer capacitors. In a second article from the same laboratory, G. A. Smolenskii et al. (Soviet Physics-Solid State 3, 714, 1961) report investigating certain solid solutions, including those of Krainik et al. Firing was similarly done in PbO. Phase transistions are discussed. In what is apparently a third article in this series, A. I. Zaslavskii et al. (Soviet Physics-Crystallography 7, 577, 1963), X-ray structural studies are reported.
Brixner U.S. Pat. No. 3,472,777 discloses the manufacture of ceramic disks by a two-step firing process. Each firing step is taught to occur in the range 800.degree.-1200.degree. C., in air. In the sole example firing was at 1050.degree. C. Brixner discloses various dielectric compositions such as PbMg.sub.1/3 Ti.sub.1/3 W.sub.1/3 O.sub.3, Pb.sub.0.8-0.9 Sr.sub.0.1-0.2 Mg.sub.1/3 Ti.sub.1/3 W.sub.1/3 O.sub.3 and Y-containing compositions.
Dielectric powder compositions capable of being fired in air (after shaping) at reduced temperatures, yet which produce high K, would permit the use of less expensive furnaces and would conserve energy and also permit the co-firing with the dielectric of low cost (but low melting) silver electrodes.